Question

The maximum contaminant level (MCL) set by the EPA of thallium in drinking water is 0.0020 mg/L . Convert the MCL of thallium from milligrams per liter to parts per billion (ppb). converted MCL of thallium: ppb A farmer recently dug a new well for his property. He sends a 16.0 mL sample of the well water to the EPA to be tested for the presence of thallium. What is the maximum amount of Tl (in μg ) that can be present in this 16.0 mL sample based on its MCL? maximum amount of Tl : μg Suppose the farmer rethinks his plan and digs a new well on the other side of his property. He sends in a new 16.0 mL sample. After testing, the EPA determines that the sample of water contains 0.00164 μg/mL Tl . Is the thallium level of the new well water safe to consume? yes not enough information no

Answer 1

a) C Tl = 2 ppb

b) mass Tl = 0.032 μg

c) yes, 0.00164 μg/mL < 0.02 μg/mL, then the water can be safely consumed.

Step-by-step explanation:

• MCL (EPA) = 0.0020 mg/L (ppm)

a) C Tl = 0,002 ppm * ( 1000ppb/ppm ) = 2 ppb

b) 16mL * ( L/1000mL ) = 0.016 L

⇒ m Tl = 0,016 L * 0.002 mg/L = 3.2 E-5 mg Tl * ( 1000μg/mg ) = 0.032μg Tl

c) C Tl = 0.00164 μg/mL

∴ according to MCL for 16 mL of sample, the maximum amount allowed is the 0.032μg Tl

⇒ the Tl concentration for 16mL of sample, would be:

⇒ C Tl = 0.032μg Tl / 16 mL = 0.02 μg Tl/mL

∴ the new sample concentration ( 0.0016 μg Tl/mL ) is less than the maximun concentration allowed by MCL ( 0.02μg Tl/mL) for that amount of sample; then the water from that well can be safely consumed.